In the automotive vehicle manufacturing industry, it is customary to “marry” the vehicle chassis to the vehicle body on a moving conveyer line. The body is typically conveyed overhead by a conveyor, and the chassis to be married to the body is supported by a moving lift machine that operates to move the chassis into position beneath the moving body while lifting the chassis into position for assembly with the body.
Lift machines may employ different lift actuators to raise and lower the platform or support upon which the vehicle chassis is supported. For example, a hydraulic cylinder can be used as the lift actuator. U.S. Pat. No. 6,109,424, hereby incorporated by reference herein, discloses the use of a push chain as the lift actuator. And, U.S. Patent Application Publication No. US 2004/0007440 A1, also hereby incorporated by reference herein, discloses the use of a spiral lift as the lift actuator.
It is desirable to provide a lift machine which is as compact and as inexpensive as possible. Employing a single lift actuator for the lift machine aids in keeping the lift machine compact and reduces the cost of the machine. However, stability of the chassis supporting platform becomes an issue when only a single lift actuator is employed. For example, in the event that the center of mass of the chassis is offset from the vertical axis of the lift actuator, a moment load is applied to the platform upon which the chassis is supported. That moment load can cause tilting of the platform and hence tilting of the chassis. Such tilting can hinder the assembly operation. It is thus desirable to provide a lift machine which employs a single lift actuator in order that the lift machine be as compact and inexpensive as possible, yet which is also stable under load.